Broadcast channel transmission and demodulation
A method and apparatus are disclosed for demodulating a NR-PBCH signal. The method may comprise receiving a primary SS and an SSS. The received SSS signal may be used as a reference signal to detect demodulation reference signals of the NR-PBCH. These demodulation reference signals may be interleaved with data on the NR-PBCH. In one method, the NR-PBCH DMRS are associated with an SSB index in an effort to improve randomization in the synchronization process. The NR-PBCH payload may be demodulated using the PSS and/or SSS and the DMRS. In one embodiment, the NR-PBCH DMRS may mapped to DMRS REs on a frequency first and time second mapping basis.
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This application is a National Stage Entry of PCT Application No. PCT/US2018/015430 filed Jan. 26, 2018 and claims the benefit of U.S. Provisional Application Ser. No. 62/454,621 filed on Feb. 3, 2017, U.S. Provisional Application Ser. No. 62/500,702 filed on May 3, 2017, U.S. Provisional Application Ser. No. 62/519,751 filed on Jun. 14, 2017 and U.S. Provisional Application No. 62/543,155 filed on Aug. 9, 2017, the contents of each of which are hereby incorporated by reference herein.
BACKGROUNDLegacy cellular systems such as 4th Generation Long Term Evolution (LTE) employ relatively simple synchronization procedures. For example, in LTE a physical broadcast channel (PBCH) always uses the same bandwidth as both a primary synchronization signal (PSS) and secondary synchronization signal (SSS). As such, in Legacy LTE systems, both are allocated in the same 6 resource blocks (RBs) in the frequency domain. Because of the frequency correlation, a receiver of a wireless transmit/receive unit (WTRU) may utilize both the PSS and SSS as a reference signal for PBCH demodulation.
However, in New Radio (NR), a NR-PBCH may consume more bandwidth and may be allocated more RBs than NR-SSS. In NR, PBCH may occupy 24 RBs compared to 12 RBs of the SSS. Therefore, in NR, SSS is no longer a good reference signal for PBCH demodulation because of the disparity in terms of frequency.
Furthermore, in LTE, PBCH may also use a common reference signal (CRS) as a reference signal for PBCH demodulation when it is present. But in NR, CRS is not present due to the fact that NR attempts to minimize an always on signal. So, CRS is no longer suitable as a reference signal for NR-PBCH demodulation. For improved performance of NR-PBCH demodulation, accurate channel estimation may be required, especially when a one-shot detection is considered. Therefore, a new reference signal (RS) design for accurate and efficient NR-PBCH demodulation may be employed for a new NR-PBCH/NR-SS structure.
SUMMARYA method and apparatus are disclosed for demodulating a New Radio PBCH (NR-PBCH) signal. The method may comprise receiving a primary SS (PSS) and a secondary synchronization signal (SSS). The received SSS signal may be used as a reference signal to detect demodulation reference signals of the NR-PBCH. These demodulation reference signals may be interleaved with data on the NR-PBCH. In one method, the NR-PBCH demodulation reference signals (DMRS) are associated with a synchronization signal block (SSB) index in an effort to improve randomization in the synchronization process.
A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings, wherein like reference numerals in the figures indicate like elements, and wherein:
As shown in
The communications systems 100 may also include a base station 114a and/or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106/115, the Internet 110, and/or the other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node-B, an eNode B, a Home Node B, a Home eNode B, a gNB, a NR NodeB, a site controller, an access point (AP), a wireless router, and the like. While the base stations 114a, 114b are each depicted as a single element, it will be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and/or network elements.
The base station 114a may be part of the RAN 104/113, which may also include other base stations and/or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, etc. The base station 114a and/or the base station 114b may be configured to transmit and/or receive wireless signals on one or more carrier frequencies, which may be referred to as a cell (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage for a wireless service to a specific geographical area that may be relatively fixed or that may change over time. The cell may further be divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, i.e., one for each sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and/or receive signals in desired spatial directions.
The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).
More specifically, as noted above, the communications system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station 114a in the RAN 104/113 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 115/116/117 using wideband CDMA (WCDMA). WCDMA may include communication protocols such as High-Speed Packet Access (HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink (DL) Packet Access (HSDPA) and/or High-Speed UL Packet Access (HSUPA).
In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A) and/or LTE-Advanced Pro (LTE-A Pro).
In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR Radio Access, which may establish the air interface 116 using New Radio (NR).
In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may implement LTE radio access and NR radio access together, for instance using dual connectivity (DC) principles. Thus, the air interface utilized by WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and/or transmissions sent to/from multiple types of base stations (e.g., a eNB and a gNB).
In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1×, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the like.
The base station 114b in
The RAN 104/113 may be in communication with the CN 106/115, which may be any type of network configured to provide voice, data, applications, and/or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have varying quality of service (QoS) requirements, such as differing throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, and the like. The CN 106/115 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and/or perform high-level security functions, such as user authentication. Although not shown in
The CN 106/115 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and/or the other networks 112. The PSTN 108 may include circuit-switched telephone networks that provide plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the transmission control protocol (TCP), user datagram protocol (UDP) and/or the internet protocol (IP) in the TCP/IP internet protocol suite. The networks 112 may include wired and/or wireless communications networks owned and/or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104/113 or a different RAT.
Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). For example, the WTRU 102c shown in
The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), a state machine, and the like. The processor 118 may perform signal coding, data processing, power control, input/output processing, and/or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit/receive element 122. While
The transmit/receive element 122 may be configured to transmit signals to, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, the transmit/receive element 122 may be an antenna configured to transmit and/or receive RF signals. In an embodiment, the transmit/receive element 122 may be an emitter/detector configured to transmit and/or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit/receive element 122 may be configured to transmit and/or receive both RF and light signals. It will be appreciated that the transmit/receive element 122 may be configured to transmit and/or receive any combination of wireless signals.
Although the transmit/receive element 122 is depicted in
The transceiver 120 may be configured to modulate the signals that are to be transmitted by the transmit/receive element 122 and to demodulate the signals that are received by the transmit/receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11, for example.
The processor 118 of the WTRU 102 may be coupled to, and may receive user input data from, the speaker/microphone 124, the keypad 126, and/or the display/touchpad 128 (e.g., a liquid crystal display (LCD) display unit or organic light-emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker/microphone 124, the keypad 126, and/or the display/touchpad 128. In addition, the processor 118 may access information from, and store data in, any type of suitable memory, such as the non-removable memory 130 and/or the removable memory 132. The non-removable memory 130 may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from, and store data in, memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).
The processor 118 may receive power from the power source 134, and may be configured to distribute and/or control the power to the other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like.
The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to, or in lieu of, the information from the GPS chipset 136, the WTRU 102 may receive location information over the air interface 116 from a base station (e.g., base stations 114a, 114b) and/or determine its location based on the timing of the signals being received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by way of any suitable location-determination method while remaining consistent with an embodiment.
The processor 118 may further be coupled to other peripherals 138, which may include one or more software and/or hardware modules that provide additional features, functionality and/or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an e-compass, a satellite transceiver, a digital camera (for photographs and/or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands free headset, a Bluetooth® module, a frequency modulated (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, a Virtual Reality and/or Augmented Reality (VR/AR) device, an activity tracker, and the like. The peripherals 138 may include one or more sensors, the sensors may be one or more of a gyroscope, an accelerometer, a hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor; a geolocation sensor; an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, and/or a humidity sensor.
The WTRU 102 may include a full duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for both the UL (e.g., for transmission) and downlink (e.g., for reception) may be concurrent and/or simultaneous. The full duplex radio may include an interference management unit 139 to reduce and or substantially eliminate self-interference via either hardware (e.g., a choke) or signal processing via a processor (e.g., a separate processor (not shown) or via processor 118). In an embodiment, the WTRU 102 may include a half-duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for either the UL (e.g., for transmission) or the downlink (e.g., for reception)).
The RAN 104 may include eNode-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the eNode-B 160a, for example, may use multiple antennas to transmit wireless signals to, and/or receive wireless signals from, the WTRU 102a.
Each of the eNode-Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and/or DL, and the like. As shown in
The CN 106 shown in
The MME 162 may be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation/deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, and the like. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and/or WCDMA.
The SGW 164 may be connected to each of the eNode Bs 160a, 160b, 160c in the RAN 104 via the S1 interface. The SGW 164 may generally route and forward user data packets to/from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring user planes during inter-eNode B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing contexts of the WTRUs 102a, 102b, 102c, and the like.
The SGW 164 may be connected to the PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.
The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or may communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which may include other wired and/or wireless networks that are owned and/or operated by other service providers.
Although the WTRU is described in
In representative embodiments, the other network 112 may be a WLAN.
A WLAN in Infrastructure Basic Service Set (BSS) mode may have an Access Point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have an access or an interface to a Distribution System (DS) or another type of wired/wireless network that carries traffic in to and/or out of the BSS. Traffic to STAs that originates from outside the BSS may arrive through the AP and may be delivered to the STAs. Traffic originating from STAs to destinations outside the BSS may be sent to the AP to be delivered to respective destinations. Traffic between STAs within the BSS may be sent through the AP, for example, where the source STA may send traffic to the AP and the AP may deliver the traffic to the destination STA. The traffic between STAs within a BSS may be considered and/or referred to as peer-to-peer traffic. The peer-to-peer traffic may be sent between (e.g., directly between) the source and destination STAs with a direct link setup (DLS). In certain representative embodiments, the DLS may use an 802.11e DLS or an 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and the STAs (e.g., all of the STAs) within or using the IBSS may communicate directly with each other. The IBSS mode of communication may sometimes be referred to herein as an “ad-hoc” mode of communication.
When using the 802.11ac infrastructure mode of operation or a similar mode of operations, the AP may transmit a beacon on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., 20 MHz wide bandwidth) or a dynamically set width via signaling. The primary channel may be the operating channel of the BSS and may be used by the STAs to establish a connection with the AP. In certain representative embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) may be implemented, for example in 802.11 systems. For CSMA/CA, the STAs (e.g., every STA), including the AP, may sense the primary channel. If the primary channel is sensed/detected and/or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.
High Throughput (HT) STAs may use a 40 MHz wide channel for communication, for example, via a combination of the primary 20 MHz channel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHz wide channel.
Very High Throughput (VHT) STAs may support 20 MHz, 40 MHz, 80 MHz, and/or 160 MHz wide channels. The 40 MHz, and/or 80 MHz, channels may be formed by combining contiguous 20 MHz channels. A 160 MHz channel may be formed by combining 8 contiguous 20 MHz channels, or by combining two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, the data, after channel encoding, may be passed through a segment parser that may divide the data into two streams. Inverse Fast Fourier Transform (IFFT) processing, and time domain processing, may be done on each stream separately. The streams may be mapped on to the two 80 MHz channels, and the data may be transmitted by a transmitting STA. At the receiver of the receiving STA, the above described operation for the 80+80 configuration may be reversed, and the combined data may be sent to the Medium Access Control (MAC).
Sub 1 GHz modes of operation are supported by 802.11af and 802.11ah. The channel operating bandwidths, and carriers, are reduced in 802.11af and 802.11ah relative to those used in 802.11n, and 802.11ac. 802.11af supports 5 MHz, 10 MHz and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support Meter Type Control/Machine-Type Communications, such as MTC devices in a macro coverage area. MTC devices may have certain capabilities, for example, limited capabilities including support for (e.g., only support for) certain and/or limited bandwidths. The MTC devices may include a battery with a battery life above a threshold (e.g., to maintain a very long battery life).
WLAN systems, which may support multiple channels, and channel bandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include a channel which may be designated as the primary channel. The primary channel may have a bandwidth equal to the largest common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and/or limited by a STA, from among all STAs in operating in a BSS, which supports the smallest bandwidth operating mode. In the example of 802.11ah, the primary channel may be 1 MHz wide for STAs (e.g., MTC type devices) that support (e.g., only support) a 1 MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and/or other channel bandwidth operating modes. Carrier sensing and/or Network Allocation Vector (NAV) settings may depend on the status of the primary channel. If the primary channel is busy, for example, due to a STA (which supports only a 1 MHz operating mode), transmitting to the AP, the entire available frequency bands may be considered busy even though a majority of the frequency bands remains idle and may be available.
In the United States, the available frequency bands, which may be used by 802.11ah, are from 902 MHz to 928 MHz. In Korea, the available frequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the available frequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidth available for 802.11ah is 6 MHz to 26 MHz depending on the country code.
The RAN 113 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 113 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, gNBs 180a, 108b may utilize beamforming to transmit signals to and/or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a, for example, may use multiple antennas to transmit wireless signals to, and/or receive wireless signals from, the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum while the remaining component carriers may be on licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement Coordinated Multi-Point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and/or gNB 180c).
The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using transmissions associated with a scalable numerology. For example, the OFDM symbol spacing and/or OFDM subcarrier spacing may vary for different transmissions, different cells, and/or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using subframe or transmission time intervals (TTIs) of various or scalable lengths (e.g., containing varying number of OFDM symbols and/or lasting varying lengths of absolute time).
The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and/or a non-standalone configuration. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c without also accessing other RANs (e.g., such as eNode-Bs 160a, 160b, 160c). In the standalone configuration, WTRUs 102a, 102b, 102c may utilize one or more of gNBs 180a, 180b, 180c as a mobility anchor point. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration WTRUs 102a, 102b, 102c may communicate with/connect to gNBs 180a, 180b, 180c while also communicating with/connecting to another RAN such as eNode-Bs 160a, 160b, 160c. For example, WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In the non-standalone configuration, eNode-Bs 160a, 160b, 160c may serve as a mobility anchor for WTRUs 102a, 102b, 102c and gNBs 180a, 180b, 180c may provide additional coverage and/or throughput for servicing WTRUs 102a, 102b, 102c.
Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and/or DL, support of network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data towards User Plane Function (UPF) 184a, 184b, routing of control plane information towards Access and Mobility Management Function (AMF) 182a, 182b and the like. As shown in
The CN 115 shown in
The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N2 interface and may serve as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling of different PDU sessions with different requirements), selecting a particular SMF 183a, 183b, management of the registration area, termination of NAS signaling, mobility management, and the like. Network slicing may be used by the AMF 182a, 182b in order to customize CN support for WTRUs 102a, 102b, 102c based on the types of services being utilized WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for machine type communication (MTC) access, and/or the like. The AMF 162 may provide a control plane function for switching between the RAN 113 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and/or non-3GPP access technologies such as WiFi.
The SMF 183a, 183b may be connected to an AMF 182a, 182b in the CN 115 via an N11 interface. The SMF 183a, 183b may also be connected to a UPF 184a, 184b in the CN 115 via an N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b and configure the routing of traffic through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions, such as managing and allocating UE IP address, managing PDU sessions, controlling policy enforcement and QoS, providing downlink data notifications, and the like. A PDU session type may be IP-based, non-IP based, Ethernet-based, and the like.
The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering downlink packets, providing mobility anchoring, and the like.
The CN 115 may facilitate communications with other networks. For example, the CN 115 may include, or may communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 115 and the PSTN 108. In addition, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which may include other wired and/or wireless networks that are owned and/or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to a local Data Network (DN) 185a, 185b through the UPF 184a, 184b via the N3 interface to the UPF 184a, 184b and an N6 interface between the UPF 184a, 184b and the DN 185a, 185b.
In view of
The emulation devices may be designed to implement one or more tests of other devices in a lab environment and/or in an operator network environment. For example, the one or more emulation devices may perform the one or more, or all, functions while being fully or partially implemented and/or deployed as part of a wired and/or wireless communication network in order to test other devices within the communication network. The one or more emulation devices may perform the one or more, or all, functions while being temporarily implemented/deployed as part of a wired and/or wireless communication network. The emulation device may be directly coupled to another device for purposes of testing and/or may performing testing using over-the-air wireless communications.
The one or more emulation devices may perform the one or more, including all, functions while not being implemented/deployed as part of a wired and/or wireless communication network. For example, the emulation devices may be utilized in a testing scenario in a testing laboratory and/or a non-deployed (e.g., testing) wired and/or wireless communication network in order to implement testing of one or more components. The one or more emulation devices may be test equipment. Direct RF coupling and/or wireless communications via RF circuitry (e.g., which may include one or more antennas) may be used by the emulation devices to transmit and/or receive data.
Based on the general requirements set out by the ITU Radio communication Sector (ITU-R), Next Generation Mobile Networks (NGMN) group and 3rd Generation Partnership Project (3GPP), a broad classification of the use cases for emerging 5G systems may be depicted as follows: Enhanced Mobile Broadband (eMBB), Massive Machine Type Communications (mMTC) and Ultra Reliable and Low latency Communications (URLLC). Different use cases may focus on different requirements such as higher data rate, higher spectrum efficiency, low power and higher energy efficiency, lower latency and higher reliability. A wide range of spectrum bands ranging from 700 MHz to 80 GHz are being considered for a variety of deployment scenarios.
It is well known that as the carrier frequency increases, the severe path loss becomes a crucial limitation to guarantee a sufficient coverage area. Transmission in millimetre wave systems could additionally suffer from non-line-of-sight losses, for example, diffraction loss, penetration loss, oxygen absorption loss, foliage loss, etc. During initial access, a base station and WTRU may need to overcome these high path losses and discover each other. Utilizing dozens or even hundreds of antenna elements to generated beam formed signal is an effective way to compensate the severe path loss by providing significant beam forming gain. Beamforming techniques may include digital, analog and hybrid beamforming.
Cell search is the procedure by which a WTRU acquires time and frequency synchronization with a cell and detects the Cell ID of that cell. LTE synchronization signals are transmitted are transmitted in the 0th and 5th subframes of every radio frame and are used for time and frequency synchronization during initialization. As part of the system acquisition process, a WTRU synchronizes sequentially to the OFDM symbol, slot, subframe, half-frame, and radio frame based on the synchronization signals. The two synchronization signals are primary synchronization signal (PSS) and secondary synchronization signal (SSS). The PSS is used to obtain slot, subframe and half-frame boundary. It also provides physical layer cell identity (PCI) within the cell identity group. The SSS is used to obtain the radio frame boundary. It also enables the WTRU to determine the cell identity group, which may range from 0 to 167.
Following a successful synchronization and PCI acquisition, the WTRU decodes the Physical Broadcast Channel (PBCH) with the help of CRS and acquire the MIB information regarding system bandwidth, System Frame Number (SFN) and PHICH configuration. It should be noted the LTE synchronization signals and PBCH are transmitted continuously according to the standardized periodicity.
It was agreed in NR that no blind detection of NR-PBCH transmission scheme or number of antenna ports is required by the WTRU. For NR-PBCH transmission, a single fixed number of antenna port(s) is supported. For NR-PBCH transmission, NR may employ both digital and analog beamforming technologies, especially for high frequency band. Digital beamforming using multi-antenna technologies and/or analog beamforming using single or multi-port beamforming technologies may be considered in NR. For reference signal of NR-PBCH demodulation, NR may employ the use of a synchronization signal (e.g. NR-SSS) or self-contained DMRS for NR-PBCH demodulation. A mobility reference signal (MRS) may also be multiplexed in an SS block if MRS is supported in an SS block. The numerology of NR-PBCH may be the same or different as that of NR-SSS. Embodiments for digital beamforming using multi-antenna technologies, analog beamforming using single or multi-port beamforming technologies or hybrid scheme that combines both digital and analog beamforming have been considered for data transmission in connected mode. The similar technologies should also be considered in idle mode or for initial access and designed for broadcast channel such as NR-PBCH for optimum system performance.
NR-PSS and/or NR-SSS may be used as a reference signal for NR-PBCH demodulation. Alternatively, a reference signal that is dedicated to NR-PBCH may be used. Such reference signal may be self-contained within NR-PBCH signal and channel. Even without an additional signal or reference signal, a receiver may still be able to demodulate an NR-PBCH signal and channel. Such reference signal for demodulation or demodulation reference signal (DMRS) is specific to NR-PBCH and may be multiplexed and embedded within NR-PBCH resources. By doing so an NR-PBCH dedicated demodulation reference signal (DMRS) may be used for NR-PBCH demodulation. The term DMRS may refer to a demodulation reference signal or demodulation reference signals as used herein.
In order to use NR-SS (either NR-PSS or NR-SSS) as a reference signal for NR-PBCH demodulation, time-division multiplexing (TDM) of NR-SS and NR-PBCH may be preferred.
Similarly,
In one or more embodiments, a hybrid dedicated demodulation reference signal (H-DMRS) may be utilized. Some of the repeated NR-PBCH dedicated DMRS may be placed in the same frequency location or subcarriers for each antenna port in order to assist CFO estimation and others of the repeated NR-PBCH dedicated DMRS may be placed in the different frequency locations or subcarriers and/or obtain frequency diversity.
In an embodiment, a non-uniform DMRS density which may employ a different density of demodulation reference signal (DMRS) may be used. In the a OFDM symbol of NR-PBCH, a higher density DMRS may be placed to assist in channel estimation. However, a lower density of DMRS may be placed in the second OFDM symbol of NR-PBCH for reducing the overhead of the DMRS. These DMRS may be the same as the DMRS for the same sub-carrier in the first OFDM symbol of NR-PBCH, which may facilitate estimation of the CFO. This may decrease the code-rate. As the second symbol is closer to the SSS, channel estimation may be supported through use of the SSS.
NR-PBCH/SS multiplexing embodiments as well as DMRS allocation embodiments may allow for both efficient and high performing NR-PBCH demodulation.
Both of these performance enhancing techniques may be realized using a hybrid DMRS mapping similar to that shown in
In one example, the NR-PSS and NR-SSS having a different bandwidth allocation compared to NR-PBCH. For example, the NR-PSS and NR-SSS may use 12 RBs, whereas PBCH uses 24 RBs. Hence there are 12 RBs of PBCH which overlaps with NR-PSS/NR-SSS and another 12 which don't overlap with NR-PSS/NR-SSS. In the receiver after the detection of cell-ID, NR-PSS and NR-SSS may be considered as known sequences that may serve as reference symbols for demodulating the overlapping RBs of the NR-PBCH. This technique may be used to improve performance and/or increase efficiency of the design. A performance improvement may be realized by allowing the NR-PSS and/or NR-SSS to assist in the channel estimation, while efficiency is realized by allowing the reduction or even full removal of the DMRS within the SS bandwidth. This concept is illustrated in
As shown in
As shown in the NR-[PBCH1 PSS SSS PBCH2] configuration 830, PSS 832 and SSS 834 are in-between PBCH1 836 and PBCH2 838. PBCH1 836 and PBCH2 838 are comprised of no or reduced density DMRS in center frequency sections 836 and 838. PBCH1 DMRS 840 and 844 may contain DMRS at full density. The same may be true for PBCH2 DMRS 842 and 846.
The DMRS density may be ⅓, ¼, ⅙ or another density depending on a chosen design. If DMRS density is ⅓, it may mean that one out of three resource elements (REs) is used for DMRS. Similarly, if DMRS density is ¼ or ⅙, it may mean that one out of four and six resource elements (REs) is used for DMRS respectively.
The various options disclosed may provide different performance advantages as well as efficiency enhancements that may be applicable in different scenarios. In order to allow for all possible options, simple signalling may be provided, for example, on the NR-SSS and/or a new radio tertiary synchronization signal (NR-TSS) to indicate which option is being used.
Examples of this non-uniform DMRS mapping of configuration 2 910 are shown in
NR-PBCH may be transmitted on N OFDM symbols. In a first embodiment, NR-PBCH coded bits are mapped across REs in N PBCH symbols, where N is the number of PBCH symbols in a NR-SS block. In a second embodiment, NR-PBCH coded bits are mapped across REs in a PBCH symbol, the NR-PBCH symbol is copied to N−1 NR-PBCH symbol in a NR-SS block.
For example, for the case where N=2, the following may be used: in the first embodiment, NR-PBCH coded bits are mapped across REs in both PBCH symbols. In the second embodiment, NR-PBCH coded bits are mapped across REs in NR-PBCH symbol, the NR-PBCH symbol is copied to the second NR-PBCH symbol NR-SS block
In the first embodiment, wherein NR-PBCH coded bits are mapped across REs in both PBCH symbols: NR-PBCH coded bits are mapped across REs in N PBCH symbols without repetition. An NR-PBCH resource may be allocated in different ways. The frequency first mapping solution may be used. The data to RE mapping may be mapped in frequency first order. RE mapping may be performed in frequency first and then time second. RE mapping in frequency may be followed by RE mapping in time. RE mapping may be applied to data, DMRS, sequence or the like. In this case, the QPSK symbols generated from data coming from the channel encoder are first mapped to first NR-PBCH OFDM symbol followed by the second or remaining N−1 NR-PBCH OFDM symbol. A time first mapping may be used. The QPSK symbols generated from data coming from channel encoder may be first mapped to a first RE of each NR-PBCH OFDM symbol followed by a second RE of each NR-PBCH OFDM symbol and so on. A hybrid method may be used where the QPSK symbols generated from data coming from channel encoder are first mapped to first (n) RB of each NR-PBCH OFDM symbol followed by second (n) RB of each NR-PBCH OFDM symbol. ‘n’ may be a predefined or configured integer known to both transmitter and receiver.
In the second embodiment, wherein NR-PBCH coded bits are mapped across REs in an NR-PBCH symbol, the NR-PBCH symbol is copied to the second NR-PBCH symbol NR-SS block, NR-PBCH coded bits are mapped across REs in a PBCH symbols with repetition. In a simple design, NR-PBCH data (and/or DMRS) may be copied on to the second or the remaining N−1 NR-PBCH OFDM symbol. In another embodiment, frequency hopping of data may be performed. The data mapped to one RB in first NR-PBCH symbol may be mapped to other RB in second NR-PBCH symbol. The pattern of this frequency hopping is known to receiver and hence it may be able to combine them increasing frequency of the decoding. The DMRS in this case may not frequency hop. Hence CFO may be estimated at the receiver using the DMRS location. In other embodiment, frequency hopping may be used only for the 12 RBs which are not overlapping with NR-PSS and NR-SSS. In one embodiment, an offset may be applied in a second PBCH symbol with respect to the first PBCH symbol. This offset may be in terms of a phase of data symbols. This phase offset may be detected at the receiver and implicit information may be decodable. For example, if the phase difference between the first and second symbols are [0, pi/2, pi, 3pi/2] 2 bits of implicit information may be indicated. It also may be possible to have a known shift which is based on cell ID. In this case, the purpose may not be to indicate anything, but rather to randomize the data using a cell-specific shift. This offset may be in terms of frequency location of the data symbols. Similar to phase, this may be cell-specific shift that may be known to increase randomization or used to blindly decode a few bits. The shift may also be a frequency shift, time shift, phase shift or the like or combination of one or more of them.
In an embodiment, a hybrid design may be implemented. In this hybrid design, the first center 12 RBs of both PBCH symbols may be filled with all the data. This data may then be copied to the side 12 RBs, for example, 6+6 on both the sides of center. This design is important as all the data symbols are present in center RBs. If SNR is good, this permits the WTRU to detect PBCH using a smaller bandwidth, for example, the 12 RBs in the middle. In this way, a WTRU only has to receive and demodulate the center 12 RB, which may also save power. Frequency hopping may or may not be used here.
If frequency hopping is used, the center part of first symbol may be copied on 12 RBs of second symbol; the center part of second symbol may be copied on 12 RBs of first symbol. As a receiver knows this pattern, it may carefully extract and assemble the DMRS block before sending to the channel decoder. This may result in a better performance at the WTRU with a lower SNR; while combining at the receiver, careful demapping of the RE is needed.
In another embodiment, a RE mapping may be as a function Cell ID and/or SS Block ID. This embodiment is motivated by the randomization of interference. Before detecting NR-PBCH, a WTRU should have detected the Cell ID using NR-PSS/NR-SSS. Also, in some cases, SS Block ID might be already known before decoding the NR-PBCH. This may be the case, for example, if TSS was transmitted and the SS Block ID was carried by TSS, or some prior knowledge about SS block index is available.
It may be desirable to use the DMRS RE mapping as a function of cell ID or SS block index or both. If the frequency location of DMRS is dependent on cell-ID, it may reduce the interference from neighboring cells. For example, this may include a shift of a location for DMRS for one, multiple or all of the OFDM symbols for NR-PBCH. In one or more embodiments, the term SS block ID, SS block index and SS block time index may be used interchangeably.
At the receiver, once a WTRU detects NR-PSS/NR-SSS, the Cell ID and/or SS Block ID is known. A WTRU may be able to identify the locations for DMRS of NR-PBCH using Cell ID and/or SS Block ID and the mapping function. The WTRU may then continue with the channel estimation for PBCH using DMRS. PBCH demodulation and decoding is then followed. As different cells are transmitting DMRS on different locations, the interference may be reduced, mitigated or avoided.
To achieve even better randomization, the sequence of DMRS (e.g., sequence or scrambling sequence) may also be dependent on cell ID or SS block index or both. The sequence of DMRS (e.g., sequence or scrambling sequence) may also be dependent on other information such as half radio frame indication, either jointly, individually or separately with SS block index or cell ID. DMRS may use any of different sequences. The options may include an M sequence, a Gold sequence, a ZC sequence or PN sequences. Different parameters of these sequences may be function of the cell ID or SS block index.
In any of the above cases, DMRS for PBCH may be also used as DMRS for PDSCH. This is true for the RBs occupied by PBCH. Rate matching may be used to convert (512) coded bits to all the used data REs which may change depending on DMRS design.
Different sequences may be used as DMRS for the NR-PBCH. One of the sequences of interest is a maximal length sequence (M-Sequence). Due to optimal noise-like characteristics and very good correlation properties, M-Sequences may serve a dual purpose. M-Sequences may be used to deliver information and also may serve as reference symbols for demodulation of the NR-PBCH.
As an example, if 24 RBs are allocated for NR-PBCH, then 2 DMRS may exist in each RB in each OFDM symbol. Hence, in each OFDM symbol 48 symbols may be needed as a DMRS. There may be a design choice to have a lower or higher number of DMRS based on a particular embodiment or implementation choice. M Sequences have lengths of 2{circumflex over ( )}M−1, making different options possible.
A higher length M-Sequence may provide for a better correlation property. These sequences may be use with different shifts. Using different shifts, it may be possible to indicate [5,6,7] bits of information implicitly using a 31, 62, or 127 M-Sequence bit length. One option may include but is not limited to indicating an SS Block index, indicating details to aid channel decoding of NR-PBCH including information about polar codes and a Beam-ID. This may further be used for any other information that needs very low latency. If SS Block ID is not indicated using the DMRS but known prior to the decoding of the NR-PBCH, the parameters like shift or the polynomial of the sequence may be a function of SS Block ID. The shift may be, but is not limited to, a frequency shift, time shift, phase shift, location shift or the like. A combination of these shift types may also be used.
In another embodiment, ZC sequences may be used as DMRS for the NR-PBCH. They may be used to deliver information using different cyclic shifts and also serve as reference symbols for demodulation of the NR-PBCH. As an example, if 24 RBs are allocated for NR-PBCH, 2 DMRS in each RB in each OFDM symbol may be had. Hence, in each OFDM symbol, N symbols may be needed for DMRS. N may be 48 in one embodiment. A length of a ZC sequence may be selected to match the number of DMRS. The best root for the ZC sequence may be determined by simulation.
It is also possible to concatenate two different ZC sequences of a same or different length. A ZC sequence may be also scrambled with another PN sequence or M sequence. Parameters, for example, a root of ZC sequence or the cyclic shift of the ZC the sequence may be a function of the cell-ID. This may enable orthogonal DMRS between different cells. The higher the length of the ZC-Sequence, the better the correlation property. These sequences may be used with different cyclic shifts. Using different shifts, it may be possible to carry [4,5,6] bits of information for 31, 62, 127 length of ZC-Sequences respectively, which may be used to indicate information to aid channel decoding of NR-PBCH, This may include information about polar encoding and/or decoding including Beam-ID. It is also possible to use different roots of ZC sequence. A WTRU may be able to blindly identify the ZC sequence used. This may be used to convey implicit information as well. This may be used for any other information that needs very low latency. If SS Block ID is not indicated using the DMRS but known prior to the decoding of the NR-PBCH, the parameters like root of ZC sequence or the cyclic shift of the ZC the sequence may be a function of SS Block ID.
For receiver processing, the following procedure may be used to detect information. A receiver may first acquire timing and frequency using NR-PSS/NR-SSS. The receiver may receive an OFDM symbol for NR-PBCH. DMRS RE allocation may be a function of cell-ID and/or SS Block ID and the DMRS RE mapping may be acquired based on the cell-ID and/or SS Block ID. The DMRS sequence may be a function of cell-ID and/or SS Block ID and a local copy of DMRS may be generated based on the cell-ID and/or SS Block ID. A local copy of DMRS may be used for channel estimation for NR-PBCH and demodulate/decode NR-PBCH.
Gold sequences may also be used for DMRS. Gold sequences may be generated by multiplying two M sequences with each other. These M sequences should be generated from irreducible primitive polynomials and both the polynomial should be preferred pair. For the design following process may be used.
Two M Sequences may be generated from preferred pair polynomial. Two different shifts are used (m0 and m1) for both. These are then XOR-ed. This sequence is BPSK modulated and then repeated or truncated to fill all DMRS.
If the chosen length of the M sequences is 31 which may be repeated, a combination of the following polynomial may be used. Octal values are in the order of 45, 75, 67.
For: g(x)=x5+x2+1
x(ī+5)=(x(ī+2)+x(ī))mod 2, 0≤ī≤25
For: g(x)=x5+x4+x3+x2+1
x(ī+5)=(x(ī+4)+x(ī+3)+x(ī+2)+x(ī))mod 2, 0≤ī≤25
For: g(x)=x5+x4+x2+x+1
x(ī+5)=(x(ī+4)+x(ī+2)+x(ī+1)+x(ī))mod 2, 0≤ī≤25
Other irreducible primitive polynomials are not excluded (Octal value 51, 37, 73). Initialization as follows may be used but other initialization may not be precluded:
x(0)=0, x(1)=0, x(2)=0, x(3)=0,x(4)=1
If the length of M Sequences 63 (for higher density DMRS) a combination of following polynomial may be used (Octal value in order are 103, 147, 155)
For: g(x)=x6+x+1
x(ī+6)=(x(ī+1)+x(ī))mod 2, 0≤ī≤56
For: g(x)=x6+x5+x2+x+1
x(ī+6)=(x(ī+5)+x(ī+2)+x(ī+1)+x(ī))mod 2, 0≤ī≤56
For: g(x)=x6+x5+x3+x2+1
x(ī+6)=(x(ī+5)+x(ī+3)+x(ī+2)+x(ī))mod 2, 0≤ī≤56
Other irreducible primitive polynomials are not excluded (Octal values 133, 141, 163). Initialization as follows may be used but other initialization may not be precluded:
x(0)=0, x(1)=0, x(2)=0, x(3)=0,x(4)=0 x(5)=1
Shifts in two sequence may be defined using the following equations. Where the s1, s2 are the two sequences of length L. m0 and m1 are two shifts. Value of n goes from 0 to L−1.
s1(m0)(n)={tilde over (s)}1((n+m0)mod L)
s2(m1)(n)={tilde over (s)}2((n+m1)mod L)
A combination function m0 and m1 may be used to indicate the following: details to aid channel decoding of NR-PBCH, which may include information about polar encoding and/or decoding; and a beam-ID.
In another option, parameters such as the polynomial of the sequence and/or the shift of the sequence(s) may be a function of the cell-ID. This may enable orthogonal DMRS between different cells. If SS Block ID is not indicated using the DMRS but known prior to the decoding of the NR-PBCH, those parameters may also be a function of SS Block ID.
For receiver processing, the following procedure may be used to detect the information: the receiver may first acquire timing and frequency using NR-PSS/NR-SSS; the receiver may receive an OFDM symbol for NR-PBCH; the DMRS RE allocation may be a function of cell-ID and/or SS Block ID and the DMRS RE mapping may be acquired based on cell-ID and/or SS Block ID; the DMRS sequence may be a function of cell-ID and/or SS Block ID, a local copy of DMRS may be generated based on cell-ID and/or SS Block ID; a local copy of DMRS may be used for channel estimation for NR-PBCH and to demodulate/decode the NR-PBCH.
The NR-PBCH may employ precoder cycling techniques to improve performance. In this case, the NR-PBCH reference signal(s), DMRS and/or SS, may or may not also be precoded using the same precoder cycling pattern as the NR-PBCH data. Assuming the same precoder is used, the precoder cycling may be applied either in the frequency domain or the time domain. For frequency domain precoder cycling some different options that may be used are detailed below:
A single precoder per NR-PBCH may be uses. A single precoder may be applied to all the RBs, for example, 24 RBs, NR-PBCH data and associated reference signals. The DMRS may be generated from a single sequence, for example, a M, ZC or Gold Sequence, since a longer sequence may improve detection performance. The DMRS may also be generated from two separate sequences split over the bandwidth.
A single precoder per RBG may be used. The RBs, along with the associated reference signals, in the PBCH may be divided into multiple RB groups (RBG) and a different precoder may be applied to each group. It should be noted that using different precoders may increase frequency diversity and hence improve performance. In general, the RBG may vary from 1 to N, where N is the number of RBs in the NR-PBCH, which in this case reverts back to the option above. The pattern may be known by the WTRU either via signaling from the SS or defined prior. Each RBG may use a different sequence; however it may be important to adjust the number of DMRS and length of sequences to match each other. Sequence length should be such that an attempt to achieve optimal correlation properties is made, and as such a particular sequence may span more multiple RBGs.
A single precoder may be used per sub-RB. In an exemplary scenario, one precoder may be used per RE, subcarrier or OFDM symbol for PBCH. A predefined precoder cycling pattern may be used across REs, subcarriers or OFDM symbols for PBCH. One precoder per DMRS group may be used. One DMRS group may be defined as half RB, partition of RB, or RE group (REG). An association between DMRS REs and data REs in a PBCH may be defined. This may also improve frequency diversity.
Precoder cycling may also be applied in the time domain. For time domain precoder cycling, some different options that may be used are detailed herein.
A single precoder may be applied for all NR-PBCH transmissions. In this case, a single precoder is applied to all PBCH data and reference signals. Different Precoders per modulo(n) NR-PBCH transmissions may be applied. In this case, a different precoder is applied for each NR-PBCH transmission per modulo(n). For example, when n=2 the following may apply: NR-PBCH transmission (0) applies precoder (0), NR-PBCH transmission (1) applies precoder (1), NR-PBCH transmission (3) applies precoder (0), NR-PBCH transmission (4) applies precoder (1), etc. Cycling may allow different WTRUs to obtain enhanced performance on different NR-PBCH transmissions based on each WTRUs unique spatial and frequency domain channel characteristics.
In each of the above cases, when there is more than one precoder being applied per NR-PBCH, the cycling pattern may be chosen to maximize the spatial and frequency diversity. In open loop schemes, this cycling pattern is pre-determined and may be chosen for example based on spatial properties for the precoder beams generated. Frequency domain characteristics may also be considered when choosing the precoder pattern in order to maximize the diversity in the frequency domain.
In order to use both NR-SS and self-contained DMRS for NR-PBCH demodulation, an indication may be introduced to indicate to a WTRU whether NR-SS and self-contained DMRS may be used jointly for channel estimation and coherent combining for NR-PBCH demodulation. A quasi-co-located (QCL) indicator may be introduced for initial access and NR-PBCH demodulation. When two signals are transmitted from two different antennas, the channels experienced by the two antennas may still have many large-scale properties in common. For example, the two signals may have the same or similar Doppler spread or shift, average delay, average delay spread or average gain, therefore they may be used by the WTRU in the setting of parameters for channel estimation. However when these two antennas are separated in distance, signals from these two antenna ports may differ even in terms of large-scale properties. A QCL indicator may be used to indicate the long-term channel properties of different antenna ports and different reference signals. For example, NR-SS and PBCH-dedicated DMRS may be assumed QCL even they are not in the same antenna port. In multiple transmission point (TRP) (multi-TRP) transmission, NR-SS and PBCH-dedicated DMRS may not be assumed QCL depending on whether or not they are in the same location or not. A QCL indicator may be indicated in NR-SS signal. If a message-based NR-SS is used, the QCL indicator may be carried by a Sync payload. If a sequence-based NR-SS is used, the QCL may be embedded in either NR-PSS or NR-SSS or combination of both. For example, different frequency and/or time relative offset may be used to indicate QCL. Different root indices or cyclic shifts of ZC sequence may be used to indicate QCL. Furthermore, different combinations of X and Y components in either NR-PSS or NR-SSS may be used to indicate QCL. Once QCL is indicated to the WTRU, the WTRU may use both NR-PSS and/or NR-SSS as combined reference signal together with NR-PBCH-dedicated DMRS for channel estimation. QCL-aided initial access and NR-PBCH demodulation may be performed. Such QCL parameters may include but not limited to Doppler spread or shift, channel average delay, channel average delay spread, channel average gain, beam correlation and spatial correlation.
Multi-antenna technologies may be used for transmission of NR-PBCH. For example, two port space frequency block coding (SFBC) and two port precoder cycling may be used as multi-antenna technologies for NR-PBCH. A single antenna port may also be used for simplicity reasons. When more than one multi-antenna technology is used for NR-PBCH, information for multi-antenna technologies used for NR-PBCH may be indicated to a WTRU. Such indication may be conveyed via NR-PSS and/or NR-SSS to indicate the one or more multi-antenna technologies or in one embodiment, a MIMO scheme or method to use for NR-PBCH. Both digital and analog beamforming technologies may be used. A hybrid digital and analog beamforming scheme may also be used.
Precoder cycling may be used as one of the indicated multi-antenna technologies. Both open-loop and semi-open loop methods may be used. A precoder using a large delay cyclic delay diversity (CDD) and/or small delay CDD, may be used. Precoder cycling patterns may be performed in time and/or frequency and may be predetermined and known to the WTRU. Both an NR-PBCH signal and a channel comprising self-contained DMRS within the NR-PBCH signal may use the same precoder sets and the same precoder cycling patterns may be applied. A gNB or TRP may perform digital beam sweeping in time and/or frequency. Digital beamforming using precoder cycling or SFBC may be combined with analog beamforming and beam sweep for NR-PBCH.
Exemplary precoder cycling designs for NR-PBCH are disclosed herein. A transmission of NR-PBCH may be based on two antenna ports with precoder cycling. The transmission on these two ports may have the same or different kinds of precoders and precoder schemes, for example, open-loop (including large delay CDD or small delay CDD), semi-open loop or the like may be utilized.
In semi open-loop, the gNB or TRP may apply a precoder, which may be expressed as W=W1·W2, where the wideband precoding matrix W1 represents the long-term statistics and the (narrow band) precoding matrix W2 represents an instantaneous channel condition. In a semi open-loop PBCH scheme, the long-term precoding matrix W1 is fed back from one or more WTRUs to the gNB. This may actually define the set of DFT beams to be used for this WTRU, implying the approximate direction of the WTRU. It should be noted that this semi open-loop procedure may work for a connected mode WTRU. If WTRUs of a cell are located in certain small range of areas of a gNB, then the semi open-loop PBCH scheme might be applied, where W1 may be determined by the WTRU locations. The gNB may then cycle the narrow band precoding matrix W2 to determine a final precoder. The cycling patterns may be in time and/or frequency domain.
A digital precoder or an analog beamformer may be used for W1 and a digital beamformer may be used for W2. One exemplary design may use analog beamforming, for example, W1 based on DFT and a digital precoder W2. Precoder cycling may be performed on W2.
In another exemplary design, a digital W1, for example, DFT-based and W2 may be used. Precoder cycling may be performed on W2 or both W1 and W2.
In another exemplary design, a digital W1, for example, a precoder codebook-based and W2 may be used. Precoder cycling may be performed on W2, or both W1 and W2. Precoder cycling may be performed on analog, digital beamforming or precoding or combination of the two.
In one embodiment, the analog beamforming circuitry may adjust beam direction and beam width for each of the antenna ports 1810 and 1816 in an SFBC scheme 1800. The control of the analog beamforming may be dependent on prior knowledge of WTRU geographic distributions. WTRU geographic distributions or beam-location profiles may be provided by WTRUs via uplink signalling or grant-free access.
Communication at frequencies above 6 GHz for 5G NR will likely rely on highly directional transmission and reception. The first steps for establishing a reliable link are the so called initial access procedures, including cell search, PBCH transmission, and an RACH procedure. The procedures associated with the current 4G LTE systems may be used as a baseline. However, since LTE is limited to below 6 GHz, directional transmission and reception is not required and is not built into these initial access procedures. Therefore new initial access procedures may need to be designed that take into account the additional complexities that are associated with directional communication systems. Each transmission and reception beam may cover a limited angular space and therefore a procedure for identifying a beam pair that may be used for communication may need to be established. This procedure may be performed via a beam sweep at the transmission and/or reception points. An addition of a beam sweep procedure may add significant complexity and power consumption, overhead, latency and the like may need to be taken into account.
A conventional beam sweep procedure may be include a TRP and WTRU “testing” all combinations of beam pairs and choosing the beam pair that may provide the best performance. The “testing” may be performed by the TRP transmitting a known sequence on a given beam while the WTRU receives a given beam and measures the resulting SINR. The measurement may be repeated for all possible beam pairs and the beam pair that returns the maximum SINR value is chosen. A framework for this type of procedure has been defined at the TRP for 5G NR as depicted in
One straightforward way to design a full beam sweep procedure using the framework defined in
An additional example of using a multi-stage TRP hierarchical beam sweep is shown in
For the first two options 2214-2216 if it is assumed there are three narrow TRP beams per wide beam, the number of beam pair measurements required is 4M+3M for option 1 and 4M+3 for option 2. This compares to the number of measurements required in the single stage exhaustive procedure where the number of measurements required is 12M. This results in an approximately 42% and 60% savings respectively. The third option 2218 combines TRP 2204 and WTRU 2206 hierarchal beam sweep. In this case, a number of measurements required is 4M+3Mnarrow. In this case, if it is assumed that M=4 and Mnarrow=3, the number of measurements required is 25. It should be noted that this case uses narrower beams in stage 2 2212 and therefore may see an additional array gain associated with the narrow beam compared to option one 2214 and option two 2216. The single stage exhaustive comparison for this option would require 12*12=144 measurements, so that this third option 2218 results in an approximately 83% savings.
Another aspect of an initial access procedure to consider is the amount of interference seen at the WTRU from other TRPs. The multi-stage procedures that were primarily used to reduce latency, power consumption, and overhead may be further modified to also address the interference issue. The main idea for reducing interference is to capitalize on the use of the multiple stages so that information from earlier stages may be used in later stages to potentially “turn off” by filtering out certain TRP beams.
The TRPs may learn or acquire the information for the detected wide beams either directly from the WTRUs via an uplink using the beam pair from the first stage or indirectly from an anchor TRP for which the WTRU is already attached. A WTRU may receive from NN narrow beams spatially contained within the WTRU wide beam detected in the first stage.
The procedure illustrated in
The advantage of the procedures above may also be seen empirically via system simulations.
There is no hierarchical sweep in two-stage TRP selective beam sweep 2402, so as mentioned above the performance is virtually identical single stage procedure above when the WTRUs are uniformly distributed. When the WTRUs are non-uniformly distributed, an SINR gain based on a reduction in the interference level may be realized. The two-stage selective non-uniform 2408 case is illustrated for comparison.
Another result shown is a two-stage TRP hierarchical selective beam sweep 2404. There is an overall gain with respect to the procedures above based on the TRP hierarchical approach using narrower beams in a second stage. There is also a gain when the WTRUs are non-uniformly distributed again based on a reduction in the interference from TRP beams being “turned off”. The two-stage selective TRP hierarchical non-uniform 2410 case is illustrated for comparison.
Another result is a two-stage TRP/WTRU hierarchical selective beam sweep 2406. There is an additional gain based on adding the WTRU hierarchical approach using again narrower beams in a second stage. There is also a gain when the WTRUs are non-uniformly distributed again based on a reduction in the interference from TRP beams being “turned off”. The two-stage selective TRP/WTRU non-uniform 2412 case is illustrated for comparison.
A straightforward full beam sweep procedure using the framework defined in
An general observation may apply to cell center WTRUs. In general, it is likely that less antenna gain may be required of the cell center WTRUs as compared to cell edge WTRUs. This is likely to be true during and before completion of the initial access procedure and in order to enable successful data transfers. Furthermore, it should be noted that multiple RF chain transmission is more feasible at the TRP than at the WTRU due to things like cost and power. With these observations in mind, a beam sweep procedure may be performed based on the transmission structure shown in
MIMO and multi-beam transmission may be enabled for initial access and in one embodiment, grant-free transmissions may be enabled for MIMO and beamforming for PBCH and subsequent DL transmission. At least one set of beamforming parameters may be provided, determined, configured, and/or known, for example, by specification. A configuration may be provided and/or transmitted, for example, by a gNB, via signaling such as broadcast or dedicated signaling. A configuration may be received by a WTRU.
A precoder may be used herein as a non-limiting example of a beamforming parameter. Some other examples include an antenna port, for example, a CSI-RS port, a set of antenna ports, a beam ID, a set of beam IDs, or the like. In the embodiments and examples described herein any other beamforming parameter may be substituted for precoder and still be consistent with one or more embodiments herein.
A WTRU may choose at least one precoder, for example, W1 or W2, from a set of precoders. A WTRU may choose a first precoder from a first set of precoders. A WTRU may choose a second precoder from a second set of precoders. The first and second set may be the same or different. A WTRU may choose a precoder that may be a preferred or recommended precoder. A WTRU may signal or indicate at least one precoder that it chooses, for example to a gNB.
A WTRU may choose a precoder for a broadcast transmission such as for a broadcast channel, for example, PBCH. A WTRU may use a first precoder for a first reception of a broadcast channel. The WTRU may determine or may know the first precoder in advance of use. The first precoder may be a default precoder that may be known by the WTRU.
The WTRU may determine the first precoder from at least one synchronization channel for example from at least one of: a time and/or frequency positions, for example, relative positions, of a first and second synchronization channel; a payload associated with a synchronization channel; or a sequence of a synchronization channel.
The WTRU may use the first precoder, for example until instructed to use another precoder. A WTRU may indicate a precoder, for example, a preferred precoder, for example for a broadcast channel. A WTRU may indicate a precoder to a gNB. The WTRU may indicate a precoder in a grant-free access that WTRU may make, for example before or without establishing an RRC connection. The WTRU may indicate a precoder in a grant-free access that WTRU may make, for example before or without establishing an RRC connection with the gNB.
A grant-free access may be a transmission using resources in time and/or frequency without a grant, for example, an explicit grant. A grant free access may be or include a random access such as a 2-step or 4-step random access. A grant-free access may be or include a 1-step transmission or a 1-step random access, for example, message 1 or only message 1 of a random access procedure.
The resources and/or preambles that may be used for the grant-free access may be configured via the broadcast channel or system information. A grant-free access may include transmission of at least one of the following: a preamble, control information, and/or a data payload. A WTRU may use a preamble, control information, and/or a data payload to indicate a selected precoder. A WTRU may expect a response or acknowledgement to a grant free access and/or to the information conveyed by the grant-free access. Alternatively, a WTRU may not expect a response or acknowledgement to a grant free access such as a grant free access that may be used to indicate a beamforming parameter.
A gNB may receive a precoder indication, for example from a WTRU. A gNB may receive a precoder indication via a grant-free access. A gNB may receive a precoder indication for a broadcast channel. A gNB may use the precoder for semi-open loop MIMO applied to a broadcast channel.
A gNB may receive a first precoder indication from a first WTRU and a second precoder indication from a second WTRU. The gNB may determine a precoder to use, for example for a broadcast channel based on the first precoder indication and the second precoder indication. The gNB may use the determined precoder, for example for the transmission of the broadcast channel.
In an example, the determined precoder may be a compromise between the first precoder and the second precoder. In another example, the first precoder may be used sometimes and the second precoder may be used sometimes. For example the gNB may cycle through a set of indicated precoders it receives from a set of WTRUs that may provide the indications on the same beam or beam set or from the same or similar direction. The gNB may alternate between a first and second indicated precoders.
A gNB may indicate a beamforming parameter such as a precoder in a response to a grant free access. The response may be via DL control information (DCI) or a DL data channel that may have an associated DCI that may indicate the resources of the DL data channel. The DCI may use a common RNTI. A WTRU may monitor for the common RNTI to receive the DCI and/or DL data.
A synchronization (sync) channel or set of synchronization channels may be used to indicate the precoder that may be used for the broadcast channel. The gNB may modify the sync channel or set of sync channel when it modifies the precoder for the broadcast channel. The modification may be to a sync channel sequence, the time and/or frequency positions, for example, using relative positions, of a first and second synchronization channel, and/or to a payload associated with a synchronization channel.
A first broadcast channel may be used to indicate the precoder and/or precoder cycling pattern that may be used for a second broadcast channel. The indication may be provided in the payload carried by the first broadcast channel.
A WTRU may use an indicated precoder and/or precoder cycling pattern for reception of a channel such as a secondary broadcast channel. The indication may be provided by a gNB. A WTRU may use a selected precoder for reception of a channel such as a broadcast channel or secondary broadcast channel. The selected precoder or precoder cycling pattern may be one that the WTRU indicated, for example in a grant-free access. The selected precoder or precoder cycling pattern may be one that the WTRU indicated, for example to a gNB.
In an example, a WTRU may use a first precoder to receive a channel such as a broadcast channel. The WTRU may use a second precoder to receive a channel, for example when reception with a first precoder may not be successful or to receive a secondary broadcast channel.
The first precoder or second precoder may be a precoder selected by the WTRU. The WTRU may use the first or second precoder after indicating the first or second precoder (e.g., to a gNB and/or in a grant-free access). The second or first precoder may be an initial precoder, a default precoder, a configured precoder, or an indicated precoder. A WTRU may use grant-free transmission to feedback at least one of the following: precoder, for example, W1 for long-term statistics; precoder, for example, W2 for short-term statistics or instantaneous channel condition; analog beamformer, for example, beam ID or a set of beam IDs; beam pair link or beam pair link set; antenna port or virtual antenna port, e.g., CSI-RS port or a set of CSI-RS ports; beam-location profile(s); ACK/NACK that responds to beam(s); WTRU beam correspondence or reciprocity; or the like.
A length-72 DMRS sequence may be generated in the case of a time duplicated sequence DMRS. This sequence may then be mapped to 72 REs DMRS of first OFDM symbol and then copied over to the second OFDM symbol. If QPSK modulation is used, length 144 sequence is generated converted to 72 QPSK symbol and mapped to all the REs of each OFDM symbol. If BPSK modulation is used, a length 72 sequence may be generated and mapped to all the REs of each OFDM symbol. In this configuration as only one sequence is generated, it may carry the SS block time index (SBTI). The terms SS block ID, SS block index and SS block time index may be used interchangeably. Different ways of SBTI indication are disclosed. As each DMRS RE is repeated in time, for a second OFDM symbol, and hence a residual CFO estimation may be performed and corrected. However, a reduced length of a sequence may reduce the detection performance of SBTI. Similar to using channel estimation to perform pre-equalization of these symbols being difficult outside of NR-PSS/NR-SSS bandwidth. This may force receiver to perform non-coherent detection and hence reducing performance.
For example, in a frequency duplicated sequence DMRS configuration, a length-72 DMRS sequence may be generated (S(1:72)). This is then mapped center 12 RB on both OFDM symbols of NR-PBCH. This same sequence also copied to the rest of the 12 RB (outside of SS Bandwidth). This may be done in few different ways.
Some exemplary embodiments 3000, 3100 are illustrated in
A potential feature of these configurations is that only the center RE may need be decoded to find the SBTI. If it is known that a channel condition is good, based on NR-PSS/NR-SSS detection, these configurations may reduce the SBTI detection complicity. In this configuration NR-PSS/NR-SSS may be used for the pre-equalization for the coherent detection of a sequence carried on the center RBs. For the RBs outside of NR-SS bandwidth, non-coherent detection may have to be performed. They may be combined with coherent detection of center RBs.
NR-PSS and NR-SSS may occupy only N REs, for example, N=127 REs in the center instead of all 144 REs of 12 RBs. Hence, good channel estimation may be performed only for 31 REs in one OFDM symbol or a total of 62 REs in two OFDM symbols. Extrapolation of the channel estimates may not perform very well. Also, this method may not allow the sub-carriers to be repeated in time and hence residual CFO estimation is not possible. Hence a modified method may be used additionally or in combination.
In one embodiment, a length-62 DMRS sequence may be mapped to the central 12 RBs on the sub-carrier which are overlapping with NR-PSS/NR-SSS, and a repeated sequence is mapped the remaining 12 RBs.
All the schemes described above had only single sequence containing the information about SBTI. Hence, for channel estimation using these DMRS is only possible after the SBTI is decoded. Hence to coherently decode SBTI, only information within SS-Bandwidth may be used. To overcome this issue, another design is disclosed. In this design, there are two sequences used. The first sequence is mapped on DMRS REs of first OFDM symbol of NR-PBCH. The second sequence is mapped on DMRS REs of the second OFDM symbol NR-PBCH.
A first sequence is generated using a Cell ID. For convenience, this is referred to as reference-DMRS. A Cell ID may be determined from the detection of NR-PSS/NR-SSS. Using the Cell ID, the first sequence may be determined. Channel estimation may be performed on those REs using the knowledge of the sequence. These channel estimates may be used to pre-equalize DMRS REs or sub-carriers. The second sequence depends on SBTI only or depends jointly on Cell ID and SBTI. As this sequence is used for indicating SBTI, as used herein the term indication-DMRS is used to refer to this sequence. After coherently detecting the second sequence, the SBTI may be decoded. This sequence may be a function of a number of variables.
In another variation of a similar concept, a known base sequence may be generated. The base is modified using the Cell ID to generate a sequence for reference-DMRS. The sequence may also be modified using SBTI to generate a sequence for indication-DMRS. The reference-DMRS is used for pre-equalization and coherently estimating the indication-DMRS and hence detecting SBTI.
These modifications as function of SBTI may be performed using some of the following ways: different initialization of linear feedback shift register (LFSR) for an M-Sequence of a gold code; a frequency or circular shift of an M sequence of a gold code; a frequency or circular shift of a gold sequence; a cyclic shift; and performing scrambling on top of original sequences.
Once NR-PSS and NR-SSS are detected, they may be used as a known sequence for channel estimation and pre-equalization for the central RBs, it may be possible to use the reference-DMRS on only RBs (or sub-carriers) not occupied by the NR-PSS/NR-SSS. Hence the indication-DMRS are mapped on first and second OFDM symbol of NR-PBCH for the bandwidth that overlaps with NR-PSS and NR-SSS. This may increase the length of a sequence used for indication-DMRS and may improve the performance of indication-DMRS.
In the design above, the first sequence is mapped on the first OFDM symbol of NR-PPBCH and second sequence is mapped on the second OFDM symbol. It also may be possible to alternate the two sequences within one OFDM symbol. Hence the sequence is mapped on DMRS REs of alternating OFDM symbols of NR-PBCH. This may improve the channel estimation performance using one of the sequences. It may also improve diversity for the second sequence and hence the detection performance of SBTI. This pattern is illustrated in
This comb pattern may be use to transmit reference-DMRS and indication-DMRS. In one design, reference-DMRS sequence may be generated using Cell ID only. This may then be modified using SBTI to generate indication DMRS sequence.
In another option, a known base sequence is generated. This sequence is modified using the Cell ID to generate sequence for reference-DMRS. The base sequence is also modified using SBTI to generate sequence for indication-DMRS.
Like the simple pattern case, a different modification as a function of SBTI may be performed in one or more of the following ways: a different initialization of a Linear Feedback Shift Register (LFSR) for an M-Sequence of a gold code; a frequency or circular shift of an M sequence of a gold code; a frequency or circular shift of a Gold sequence; a cyclic shift; and/or a scrambling on top of one or more original sequences.
Like the simple pattern case, NR-PSS and NR-SSS may be used for channel estimation and pre-equalization for the central RBs. It is possible to use the reference-DMRS only on the RBs (or sub-carriers) not occupied by the NR-PSS/NR-SSS. Hence the indication-DMRS are mapped on a first and second OFDM symbol of NR-PBCH for the bandwidth that overlaps with NR-PSS and NR-SSS. This may increase the length of a sequence used for indication-DMRS and hence may improve the performance of indication-DMRS.
Short LFSR gold sequences may be implemented with shift registers. In this way, different length shift registers may be used to generate the gold sequence. For example, if short length lf LFSR of length 7 is used:
c(n)=(x1(n)+x2(n))mod 2
x1(n+7)=(x1(n+4)+x1(n))mod 2
x2(n+7)=(x2(n+1)+x2(n))mod 2
One or both the m-sequences may be initialized with the state x(0)=0, x(1)=0, x(2)=0, . . . ,x(5)=0 x(6)=1. If only one LFSR is initialized with [00001], another LFSR may be initialized using SS Block Time index or Cell ID or combination of both.
A long LFSR Gold sequence may be used in addition or combination. A long LFSR gold sequence may also be generated via a longer shift register and a shift (Nc) while selecting the output may be used to select the part of gold sequence of desired length.
c(n)=(x1(n+NC)+x2(n+NC))mod 2
x1(n+31)=(x1(n+3)+x1(n))mod 2
x2(n+31)=(x2(n+3)+x2(n+2)+x2(n+1)+x2(n))mod 2
Nc may be defined as an integer. For eg: NC=1600.
A very long LFSR gold sequence, for example of length 64, may also be generated by longer shift register and a shift (Nc) while selecting the output may be used to select the part of gold sequence of desired length.
c(n)=(x1(n+NC)+x2(n+NC))mod 2
x1(n+63)=(x1(n+1)+x1(n))mod 2
x2(n+63)=(x2(n+38)+x2(n+13)+x2(n+1)+x2(n))mod 2
In this example, n=01, 2, 3 . . . . NREDMRS−1. Here Nc may be much larger integer number and may be found experimentally to find good correlation sequences.
Any of the above sequences may have scrambling applied on top before modulation (BPSK/QPSK). The scrambling code may be generated from similar length LFSR.
Cyclic shifts may be applied to any of the Gold sequences after modulation (BPSK/QPSK).
A cyclic shift may be of the form
where m=0, 1, . . . M−1 and i is the shift index. In this example, seq is the original modulated sequence and seq, is the sequence with cyclic shifts.
Modulation is used for the sequences and all of the above sequences may be BPSK or QPSK modulated.
Using BPSK, r(m)=(1−2·c(m)) m=0, 1, . . . , NREPBCH−1.
Using QPSK, every two bits may be combined into one symbol
Bits which are at a NREPBCH distance apart, may be combined into one symbol,
In an embodiment, a NR-PBCH DMRS time block ID indication/detection may be implemented. A different initialization of M-Sequence LFSR may be performed.
As an example, consider the gold code defined by:
c(n)=(x1(n)+x2(n))mod 2
(n+7)=(x1(n+4)+x1(n))mod 2
x2(n+7)=(x2(n+1)+x2(n))mod 2
x1 is first m sequence and x2 is second m sequence to generate the gold code. The LFSR to generate one or both m-Sequences x1, x2 used to generate the gold code may be initialized using SBTI or Cell ID or combination of both or combination of even more number of variables such as RNTI, slot number, cell ID, half frame.
Different examples of these initializations are enumerated below:
Option 1: cint=NIDcell. Option 2: cint=mod(NIDcell,x), where x is a known integer. Option 3: cint=2x NIDcell−1 (x is an integer <Llfsr-1-10), as 10 bits are used to indicate NIDcell. Option 4: cint=2x·(2·NIDcell+1)+2·sbti−1. Option 5 may be more generalized option of option 5. cint=2x1·(x2·NIDcell+x3)+x4·sbti+x5, where x1 to x5 may be determined imperially to have best correlation properties. More options are also possible.
It may also be possible to generate two different gold sequences using two different initializations. For Example, a first shift resulting in reference-DMRS may be used for pre-equalization and another shift resulting in indication-DMRS may be used for indicating the SBTI.
If only one sequence is used, partial coherent/partial non-coherent detection may be performed. Different hypothesis of gold sequences be generated (using different initialization of M sequences) at the receiver to detect SBTI.
A frequency or circular shift of individual M sequence may be applied.
c(n)=(xm01(n)+xm12(n))mod 2
x1(n+7)=(x1(n+4)+x1(n))mod 2 x1(m0)(n)=x1((n+m0)mod L)
x2(n+7)=(x2(n+1)+x2(n))mod 2 where x2(m1)(n)=x2((n+m1)mod L)
Circular shift values m0,m1 are jointly or individually determined by a Cell ID and/or SBTI. Knowing the relations between the Cell ID SBTI and m0, m1, and the knowledge of Cell ID from detection of PSS/SSS, a hypothesis may be generated for SBTI, and may be used to detect which SBTI was indicated in the gold code.
It may be possible to generate two different gold sequences using two different circular shifts in M sequences. First shift resulting in reference-DMRS used for pre-equalization and another shift resulting in indication-DMRS used for indicating the STBI. If only one sequence is used, partial coherent/partial non-coherent detection may be performed. Different hypothesis be generated (using different frequency shift of individual M-Sequences) at the receiver to detect STBI.
A frequency or circular shift of a gold sequence may be:
r=c((n+m0)mod L)
c(n)=(x1(n)+x2(n))mod 2
x1(n+7)=(x1(n+4)+x1(n))mod 2
x2(n+7)=(x2(n+1)+x2(n))mod 2
Circular shift values m0 may be determined by the Cell ID and/or SBTI. Knowing the relations between the Cell ID SBTI and m0, and the knowledge of Cell ID from detection of PSS/SSS, a hypothesis may be generated for SBTI. And detect which SBTI was indicated by the gold code. This is a special case of the ‘Circular shift of individual M sequence’ where both sequence have same shift. (m0=m1).
It may be possible to generate two different gold sequences using two different circular shifts in frequency. One used for pre-equalization and another for indicating the SBTI.
If only one sequence is used, partial coherent/partial non-coherent detection may be performed. A different hypothesis may be generated, for example using a different frequency shift of this gold sequence, at the receiver to detect STBI.
In the above equation, NRBPBCH=24 denotes the assigned bandwidth in resource blocks of the NR-PBCH transmission. The pseudo-random sequence c(i) is may be defined according to one or more embodiments described herein.
A second sequence (Indication DMRS) is generated using following procedure: The demodulation reference-signal for a second OFDM symbol of NR-PBCH is generated with cyclic shifts to the sequence of first symbol.
In this example, k=2 or 3 depending on how many bits needs to be indicated for SS Block timing index. These sequences may be mapped in a simple pattern of a comb pattern. Due to the circular nature of cyclic shifts, every 8th tone of both the reference-DMRS and indication-DMRS will be identical. This property be used to estimate CFO at the receiver and the cyclic shift may be used to estimate the SBTI.
The CFO estimation may be performed using:
where fc is carrier frequency, ΔnOFDM=2 (distance been two OFDM symbols). This property illustrated below.
As an example
for m=0:17 is shown in
The 8 rows (rows 0-8) shown in
The cyclically shifted DMRS may also be taken to the time domain. The phase shift in frequency domain translates to time-index-offset in time domain. This may result in faster detection of SBTI (without multiple hypothesis testing).
Hence a ratio of (DMRSpbch2/DMRSpbch1) is a differential estimation free of channel (if channel hasn't changed much from one symbol to other). IFFT of these ratios for each STBI are time shifted version of each other. Hence coherent detection of SBTI may be performed quickly and with lower complexity.
A scrambling sequence, which may be a function of SBTI, may be applied to the reference-DMRS to generate indication-DMRS. Using the scrambling pattern known at receiver, hypothesis to find SBTI may be generated and hence SBTI may be detected.
The transmit power of REs for PBCH DMRS could be higher than that of REs for PBCH data. To achieve this, power boosting with a known factor could be applied for PBCH DMRS transmission. Knowledge of this factor at receiver may be important.
Although the features and elements of the present invention are described in the preferred embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the preferred embodiments or in various combinations with or without other features and elements of the present invention. Although each one of the beams shown in the FIGs may be illustrated as to a particular direction, it should be kept in mind that this is for illustration purposes and a limitation with respect to a particular beam format, width or orientation is not intended.
Although the embodiments described herein consider LTE, LTE-A, New Radio (NR) or 5G specific protocols, it is understood that the embodiments described herein are not restricted to this scenario and are applicable to other wireless systems as well.
Although features and elements are described above in particular combinations, one of ordinary skill in the art will appreciate that each feature or element can be used alone or in any combination with the other features and elements. In addition, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over wired or wireless connections) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.
Claims
1. A method performed by a wireless transmit/receive unit (WTRU), the method comprising:
- demodulating a payload of a physical broadcast channel (PBCH) transmission, using a demodulation reference signal (DMRS), in at least a second, in time, OFDM symbol, and a fourth, in time, OFDM symbol of a synchronization signal block (SSB), wherein the DMRS is located in same subcarriers in the second, in time, OFDM symbol and the fourth, in time, OFDM symbol and is interleaved in frequency with the payload of the PBCH;
- wherein the SSB includes a primary synchronization signal (PSS) in a first, in time, OFDM symbol of the SSB and a secondary synchronization signal (SSS) in a third, in time, OFDM symbol of the SSB;
- wherein the SSB spans only the first, in time, OFDM symbol, the second, in time, OFDM symbol, the third, in time, OFDM symbol and the fourth, in time, OFDM symbol;
- wherein the PSS and the SSS span a same frequency spectrum and the PBCH spans a wider frequency spectrum than the PSS and the SSS.
2. The method of claim 1, further comprising demodulating the payload of the PBCH using the PSS and/or the SSS and the DMRS.
3. The method of claim 1, wherein the subcarriers in which the DMRS is placed are based on a cell identification (ID).
4. The method of claim 3, wherein the DMRS is derived from a scrambling sequence based on the cell ID and an SSB index.
5. The method of claim 1, wherein the DMRS is based on a gold sequence used by the WTRU as a reference signal (RS) for PBCH demodulation and for SSB time index detection.
6. The method of claim 4, wherein 2 bits are used as an SSB index.
7. The method of claim 4, wherein 3 bits are used as an SSB index.
8. The method of claim 1, wherein the SSB spans only the first, in time, OFDM symbol, second, in time, OFDM symbol, third, in time, OFDM symbol and fourth, in time, OFDM symbol.
9. A wireless transmit/receive unit (WTRU) comprising:
- a demodulator configured to use a demodulation reference signal (DMRS) to demodulate a payload of a physical broadcast channel (PBCH) transmission in at least a second, in time, OFDM symbol and a fourth, in time, OFDM symbol of a synchronization signal block (SSB), wherein the DMRS is located in same frequency locations in the second, in time, OFDM symbol and the fourth, in time, OFDM symbol and is interleaved in frequency with the payload of the PBCH;
- wherein the SSB includes a primary synchronization signal (PSS) in a first, in time, OFDM symbol of the SSB and a secondary synchronization signal (SSS) in a third, in time, OFDM symbol of the SSB, wherein the DMRS is located in same frequency locations in the second, in time, OFDM symbol and the fourth, in time, OFDM symbol and is interleaved in frequency with the payload of the PBCH;
- wherein the SSB spans only the first, in time, OFDM symbol, the second, in time, OFDM symbol, the third, in time, OFDM symbol and the fourth, in time, OFDM symbol;
- wherein the PSS and the SSS span a same frequency spectrum and the PBCH spans a wider frequency spectrum than the PSS and the SSS.
10. The WTRU of claim 9, wherein the demodulator is configured to demodulate the payload of the PBCH using the PSS and/or the SSS and the DMRS.
11. The WTRU of claim 9, wherein subcarriers in which the DMRS is placed are based on a cell identification (ID).
12. The WTRU of claim 11, wherein the DMRS is derived from a scrambling sequence based on the cell ID and an SSB index.
13. The WTRU of claim 9, wherein the DMRS is based on a gold sequence used by the WTRU as a reference signal (RS) for PBCH demodulation and for SSB time index detection.
14. The WTRU of claim 12, wherein 2 bits are used as an SSB index.
15. The WTRU of claim 12, wherein 3 bits are used as an SSB index.
16. A wireless transmit/receive unit (WTRU) comprising:
- a receiver configured to receive a synchronization signal block (SSB), wherein the SSB includes:
- a primary synchronization signal (PSS) located in a first, in time, orthogonal frequency division multiplexing (OFDM) symbol of the SSB;
- physical broadcast channel (PBCH) information located in at least a second, in time, OFDM symbol of the SSB and a fourth, in time, OFDM symbol of the SSB, wherein a demodulation reference signal (DMRS) is located in same frequency locations in the second, in time, OFDM symbol and the fourth, in time, OFDM symbol and is interleaved in frequency with a payload of the PBCH; and
- a secondary synchronization signal (SSS) located in a third, in time, OFDM symbol of the SSB;
- wherein the SSB spans only the first, in time, OFDM symbol, the second, in time, OFDM symbol, the third, in time, OFDM symbol and the fourth, in time, OFDM symbol;
- wherein the PSS and the SSS span a same frequency spectrum and the PBCH spans a wider frequency spectrum than the PSS and the SSS.
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Type: Grant
Filed: Jan 26, 2018
Date of Patent: Mar 26, 2024
Patent Publication Number: 20190357159
Assignee: InterDigital Patent Holdings, Inc. (Wilmington, DE)
Inventors: Kyle Jung-Lin Pan (Saint James, NY), Fengjun Xi (San Diego, CA), Steven Ferrante (Doylestown, PA), Chunxuan Ye (San Diego, CA), Janet A. Stern-Berkowitz (Little Neck, NY), Nirav B. Shah (San Diego, CA)
Primary Examiner: Rasheed Gidado
Application Number: 16/482,871
International Classification: H04W 56/00 (20090101); H04L 1/00 (20060101); H04L 1/18 (20230101); H04L 1/1829 (20230101); H04L 5/00 (20060101); H04L 5/10 (20060101); H04W 72/04 (20230101); H04W 72/044 (20230101);
